Ruby on Rails, or Rails, is a server-side web application framework written in Ruby under the MIT License. Rails is a model–view–controller (MVC) framework, providing default structures for a database, a web service, and web pages. It encourages and facilitates the use of web standards such as JSON or XML for data transfer and HTML, CSS and JavaScript for user interfacing. In addition to MVC, Rails emphasizes the use of other well-known software engineering patterns and paradigms, including convention over configuration (CoC), don't repeat yourself (DRY), and the active record pattern.
Ruby on Rails' emergence in 2005 greatly influenced web app development, through innovative features such as seamless database table creations, migrations, and scaffolding of views to enable rapid application development. Ruby on Rails' influence on other web frameworks remains apparent today, with many frameworks in other languages borrowing its ideas, including Django in Python; Catalyst in Perl; Laravel, CakePHP and Yii in PHP; Grails in Groovy; Phoenix in Elixir; Play in Scala; and Sails.js in Node.js.
Well-known sites that use Ruby on Rails include Airbnb, Bloomberg, Crunchbase, Dribbble, and GitHub.
Ruby on Rails evolves radically from release to release exploring the use of new technologies and adopting new standards on the Internets. Some features are very stable in Ruby on Rails while some are replaced in favour of new techniques.
The model–view–controller (MVC) pattern is the fundamental structure to organize application programming.
In a default configuration, a model in the Ruby on Rails framework maps to a table in a database and to a Ruby file. For example, a model class User will usually be defined in the file 'user.rb' in the app/models directory, and linked to the table 'users' in the database. While developers are free to ignore this convention and choose differing names for their models, files, and database table, this is not common practice and is usually discouraged in accordance with the "convention-over-configuration" philosophy.
A controller is a server-side component of Rails that responds to external requests from the web server to the application, by determining which view file to render. The controller may also have to query one or more models for information and pass these on to the view. For example, in an airline reservation system, a controller implementing a flight-search function would need to query a model representing individual flights to find flights matching the search, and might also need to query models representing airports and airlines to find related secondary data. The controller might then pass some subset of the flight data to the corresponding view, which would contain a mixture of static HTML and logic that use the flight data to create an HTML document containing a table with one row per flight. A controller may provide one or more actions. In Ruby on Rails, an action is typically a basic unit that describes how to respond to a specific external web-browser request. Also, note that the controller/action will be accessible for external web requests only if a corresponding route is mapped to it. Rails encourages developers to use RESTful routes, which include actions such as create, new, edit, update, destroy, show, and index. These mappings of incoming requests/routes to controller actions can be easily set up in the routes.rb configuration file.
A view in the default configuration of Rails is an erb file, which is evaluated and converted to HTML at run-time. Alternatively, many other templating systems can be used for views.
Ruby on Rails includes tools that make common development tasks easier "out-of-the-box", such as scaffolding that can automatically construct some of the models and views needed for a basic website.[41] Also included are WEBrick, a simple Ruby web server that is distributed with Ruby, and Rake, a build system, distributed as a gem. Together with Ruby on Rails, these tools provide a basic development environment.
